This invention relates to selective call receivers, such as pagers, operating in a communication environment. In particular, this invention relates to, but is not necessarily limited by, channel monitoring by a multichannel selective call receiver operating in a communication environment.
Selective call receivers, such as pagers, of a selective call system receive information transmitted on carrier frequencies or channels within a communication environment. Such information is typically formatted according to messaging protocols defined for the selective call system. For example, Motorola""s FLEX(trademark) selective call system has a messaging protocol in which information is grouped into frames which are then A transmitted as a cycle. A FLEX(trademark) cycle has one hundred and twenty eight frames of which some are mandatory frames transmitted at the start of the FLEX(trademark) cycle. Each of the mandatory frames is divided into information fields. Information fields at the start of a mandatory frame can point to more information for a selective call receiver in the rest of the mandatory frame. For example, the address field can address one or more selective call receivers which will have more information provided by the rest of the mandatory frame.
Receiving information from a FLEX(trademark) cycle requires a selective call receiver to synchronize to the FLEX(trademark) cycle to monitor for the information. Synchronizing has to be attained at or before the mandatory frames to receive information from the information fields of such frames. Upon processing the mandatory frames, other information, such as assigned frames that provide information specifically for the selective call receiver, can be determined to receive more information from the FLEX(trademark) cycle. In a FLEX(trademark) communication environment that supports multichannel selective call receivers, FLEX(trademark) cycles are synchronously transmitted on different channels by referencing such cycles to external time signals provided by, for example, a Global Positioning System. These multichannel selective call receivers are supported by what is referred to as a FLEX(trademark) roaming system. Channels for multichannel selective call receivers in the FLEX(trademark) roaming system are also known as roaming channels.
Determining which channel to monitor is critical for multichannel selective call receivers in a FLEX(trademark) roaming system as information can be received from different FLEX(trademark) cycles transmitted concurrently on different roaming channels. Each of these different roaming channels should be monitored quickly as there can be a problem of not detecting information transmitted on another. Furthermore, invalid channels which are not roaming channels of the FLEX(trademark) roaming system can provide FLEX(trademark) cycles that may be inadvertently detected. Such invalid channels should be quickly distinguished from valid channels that can provide information to the multichannel selective call receivers.
It is an object of this invention to overcome or at least alleviate at least one of the problems associated with channel monitoring by a multichannel selective call receiver operating in a communication environment.
According to one aspect of the invention, there is provided a multichannel selective call receiver comprising:
a receiver for receiving information on a channel, said information being formatted as a cycle having a plurality of frames including at least one mandatory frame having an address field; and
processing means coupled to said receiver,
wherein said processing means is adapted to control said receiver to receive information on other channels within said mandatory frame when said address field does not address said multichannel selective call receiver in said mandatory frame.
Preferably, said processing means can be further adapted to control said receiver to receive information on said other channels following said address field and within said mandatory frame.
Suitably, said processing means can comprise a controller coupled to a baud detector, said controller being adapted to control said baud detector to perform baud detection of information.
Preferably, said processing means can further comprise a timer for determining lapse of a predetermined time period, said timer being associated with said baud detector.
Suitably, said processing means can comprise a memory for storing a channel list indicative of channel priority of said channel and said other channels.
According to another aspect of the invention, there is provided a method for channel monitoring by a multichannel selective call receiver, said method comprising the steps of:
receiving information on a channel, said information being formatted as a cycle having a plurality of frames including at least one mandatory frame having an address field; and
controlling said receiver to receive information on other channels during said mandatory frame when said address field does not address said multichannel selective call receiver in said mandatory frame.
Preferably, said step of controlling can comprise the step of determining whether remaining duration of said mandatory frame is sufficient for a baud detection.
Suitably, said step of controlling can further comprise the step of selecting a next channel for said baud detection when remaining duration of said mandatory frame is sufficient, said next channel being of a higher or equal priority as indicated within a channel list stored in a memory.
Preferably, said step of controlling can further comprise the step of marking said next channel for a synchronization field sample when said baud detection determines that said next channel may be a valid channel.
Suitably, said step of controlling can further comprise the step of sampling a synchronization field of a next available mandatory frame of said next channel.